Maximum-current-indicating device.



No. 793,491. PATENTEU JUNE 27, 1905. M. J. WUEL.

MAXIMUM CURRENT INUIGATING DEVICE.

APPLICATION FILED NOV. 21,1904.

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A C f U /ryventor Maur/ce 1 Wohl UNITED STATES Patented .Tune 27, 1905.

PATENT OFFICE.

ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

NIAXIMUNl-CURRENT-'INDICATING DEVICE.

SPECIFICATION forming part of Letters Patent No. 793,491, dated J une 27, 1905.

Application inea Nvemiier 21,1904. serai Nt. 233,623.

To all whom it may concern.-

Be it known that I, MAURICE J. WoHL, a citizen of the United States, residing at Brooklyn, county of Kings', State of New York, have invented certain new and useful Improvements in Maximum-Current-Indicating Devices, of which the following is a specification.

My invention relates to current-indicating devices for electric circuits; and its object is to provide a simple, economical, efiicient, and reliable device for indicating the maximum amount of current that has traversed an electric circuit within a given time.

By my invention all moving parts are eliminated, and the construction of the device is thelreby rendered simpler and more economica My invention consists in the combination, with a conductor adapted to be heated by the flow of current, of material adapted to bediscolored or to be caused to undergo some other visible physical or chemical change by the heat from the conductor, the conductor and the sensitized material being so arranged that different portions of the sensitized material are unequally affected by a given current through the conductor. Thus the sensitized material may be arranged with its several portions at equal distances from a uniform conductor or the material may be arranged at a uniform distance from a conductor, so arranged that different portions are unequally heated by the same current.

My invention will best be understood by reference to the accompanying drawings, in which- Figure 1 shows a front elevation ofa lnaximum-currentindicating device arranged in accordance with my invention. Fig. 2 shows a side elevation of the same. Fig. 3 shows a front elevation of a modified form, and Fig. L shows a side elevation of the same.

In Figs. 1 and Q, A represents a suitable casing, within which is mounted a strip B, stretched between the supporting-pins I) b and carrying a material adapted to be affected visibly by heat. For this purposeIhave found that a ten-per-cent. solution of sulfuric acid containing a little sugar, applied to a strip of non-absorbent paper or cardboard, is especially suitable. Other materials-such, for instance, as a saturated solution of bicarbonate of soda-may be employed. C represents a scale which is placed adjacent to the sensitized strip B. This strip lmay be calibrated in amperes, so that the discoloration or other change-in the sensitized strip for a given portion of its length will correspond to acurrentiiow of a given amount, as indicated .on the scale C. Adjacent to sensitized strip B and at an angle to the plane of the strip is the hot wire D, which is stretched between the supporting-posts b d. It is evident that if this wire is of uniform diameter and is traversed by a given current the wire will be uniformly heated, and since the wire makes an angle with the plane of the sensitized strip the several portions of the sensitized strip will be unequally heated by the current in the wire. Consequently a discoloration of the strip will be produced, beginning at its left-hand end and extending a distance depending upon the heat of the wire D. The length of this discoloration or other change, as measured by the scale C, will give the maximum current-How through the circuit in which the wire D is connected.

I have shown the device provided with suitable binding-posts E, which are connected'by the leads e e to the supporting-posts Z d for the hot wire.

Instead of arranging the sensitized material at an angle to the heated conductor the conductor and strip may be placed parallel to each other and the heated conductor so arranged that it will be unequally heated throughout its length, the only necessary condition being that the several portions of the sensitized material shall be unequally heated by a given current in the conductor. Such an arrangement is shown in Fig. 3, in which in place of a hot wire of uniform cross-section aflat triangular conductor F is employed. It is evident that a given current strength will produce a greater heat near the apex of 95 the triangle than near the base, and this difference in heat may be utilized to produce a change in the sensitized material supported at a uniform distance from the conductor. This sensitized material may be applied to a strip mounted parallel with the fiat conductor F, or it may be applied directly to the conductor as a coating. In either case a scale C, arranged as shown, will indicate the maximum current-flow through the conductor.

Other modifications may be made in the arrangement Of the device, and consequently I do not desire to limit myself to the particular construction and arrangement of parts here shown, but aim in the appended claims to Coverall modications which are Within the scope of my invention.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

1. In a maXimum-current-indicating device, a conductor, and material disposed adjacent to the conductor adapted to be affected visibly by heat due to the flow of current in the conductor, said conductor and said material being so disposed that different portions oi' the material are unequally heated by a given current-How in the conductor.

2. In a maXimum-current-indicating device, material adapted to be affected visibly by heat, and means for producing an unequal heating of different portions of said material for a given iiow of current through the device.

3. In a maXimum-current-indicating device, material adapted to be affected visibly by heat, means for lproducing an unequal heating of different portions of said material for a given .iiow of current throughthe device, and a graduated scale adjacent to the unequally-heated portions of said material.

4. In a maximum-current*indicating device, a strip coated with a material adapted to be discolored by heat, and a conductor adjacent to said strip arranged to produce an unequal heating of different portions of said strip for a given HOW of current through the conductor. I

5. In a maximum-current-indicating device, a strip coated with a Weak solution of sulfuric acid and sugar, and a conductor adjacent to said strip arranged to produce an unequal heating of different portions of said strip for a given HOW of current through said conductor.

6. In a maximum-current:indicating device, a strip coated with a weak solution of sulfuric acid and sugar, a conductor adjacent to said strip arranged to produce an unequal heating Ot' diierent portions of said strip for a given flow of current through said conductor, and a graduated scale adjacent to said.

strip.

In Witness whereof I have hereunto set my hand this 11th day of November, 1904.

MAURICE J. WOHL. Witnesses:

WM. P. COOK, GEORGE EBELING. 

